The present invention relates generally to an apparatus for testing the chipping resistance and adherence of surface coatings. More particularly, the invention relates to a gravelometer having multi-standard capabilities so that a user need not purchase a plurality gravelometers each dedicated to a particular testing standard. In accordance with the present invention, a gravelometer base unit selectively receives one of a plurality of target chambers to enclose the sample being tested, and one of a plurality of media guns for propelling the media at the test sample secured in the target chamber. The particular target chamber and media gun utilized depend upon the particular testing standard to be followed.
Gravelometers and their use for testing the adhesion and chip resistance of coatings to a test panel or other specimen are generally well known. Typically, the gravelometer is adapted to project a specified volume of standardized blasting media, such as gravel, split shot, buck shot, sand, or the like, at a test panel or other object coated with the paint or other coating being tested. The test panel is housed in or otherwise surrounded by a xe2x80x9ctarget chamberxe2x80x9d so that the media is contained for safety. The media is typically propelled toward the test specimen from a media xe2x80x9cgunxe2x80x9d under the Force of compressed air at a specified pressure and flow rate. Media is fed into the media gun in a controlled manner either manually or through use of an automatic feeding apparatus. Once the supply of media is exhausted, the test panel is removed from the target chamber, examined, and evaluated in accordance with particular chipping and adherence standards.
In the United States of America, gravelometers, their use, and test specimen evaluation, are generally carried out in accordance with Recommended Practice SAE J400 of the Society of Automotive Engineers (SAE J400). In general, SAE J400 specifies test equipment, test conditions, test procedures, and test specimen evaluation. More particularly, SAE J400 specifies the use of a particular media (standardized gravel), a particular compressed air gun for projecting the gravel, a particular distance between the test specimen and the gun, particular angular orientations of the test specimen relative to the projection path of the media, and other testing parameters. As such, heretofore, those desiring to test coatings in accordance with SAE J400 were required to purchase a dedicated SAE J400 compliant gravelometer not usable to conduct testing in accordance with any other standard.
Likewise, those desirous of testing a specimen in accordance with a common European standard established by Verband der Automobilindustrie (VDA), had to purchase a dedicated VDA compliant gravelometer. The SAE J400 and VDA standards use different media and different types of media guns. Therefore, neither a dedicated SAE J400 gravelometer nor a dedicated VDA gravelometer is usable to conduct coating tests under a different standard.
In addition to being generally inconvenient, the need to purchase, operate, and maintain multiple prior gravelometers was found to be quite expensive and generally undesirable. Also, the multiple gravelometers consume large amounts of valuable shop floor space.
Another problem associated with prior gravelometers is their inability to receive and contain large three-dimensional test specimens. For example, with coatings, it is often desirable to test the chipping resistance after the coating has been applied to an actual end product such as a wheel, a spring, or an automobile body part. With prior gravelometers, their is no convenient and effective way of subjecting such three-dimensional objects to a test without departing from the test procedures or without purchasing yet another specialized gravelometer made for such parts.
The present invention therefore relates to a gravelometer which is able to belconfigured with any one of a plurality of target chambers and media guns to comply with SAE J400, VDA, or any other testing standard.
In accordance with a first aspect of the invention, a gravelometer apparatus includes a media gun mount extending from a frame member. The gun mount includes a bore adapted to receive a barrel of an associated media gun and a media gun fastening device for fixedly and releasably securing the media gun relative to the mount so that the gun barrel is placed in the bore. A first enclosed target chamber is releasably secured to the frame member in an operative position so that the barrel of an associated media gun secured to the frame member is directed into an enclosed interior space of the target chamber through an inlet. The target chamber includes a target support for fixedly retaining a target specimen in an operative position so that testing media projected outwardly from an outlet in the barrel of the associated gun impinges upon the target specimen and is retained in the enclosed interior space. A media supply system is connected to the frame member and included a media hopper and a media feeder for conveying media from the hopper to a media inlet of the associated media gun.
In accordance with another aspect of the present invention, a multi-test gravelometer for performing coating testing operations based on at least two different standards includes a frame adapted for releasably receiving and retaining an associated one of at least first and second media guns in an operative position so that a media inlet of the gun is positioned to receive testing media and a media outlet of the gun is positioned to project testing media toward a testing target. A compressed air supply is adapted for communication with an air inlet of the gun. The gravelometer includes means for selectively and releasably connecting one of a plurality of different two-dimensional specimen target chambers to the frame by in an operative position so that the media outlet of the gun is directed into and enclosed by an interior portion of the target chamber in line with a target specimen support region thereof.
In accordance with still another aspect of the present invention, a modular gravelometer apparatus includes a base unit having a frame. A compressed air tank is secured to the frame. A plurality of different media guns, each conformed in accordance with a particular testing standard, are adapted for individual and selective operative securement to the base unit frame by at least one releasable connector. Each of the media guns includes a media inlet adapted to receive testing media, a media outlet for projecting the testing media outwardly along a target path, and a compressed air inlet adapted for selective fluid communication with the compressed air tank. A plurality of different two-dimensional specimen target chambers are each conformed in accordance with one of the testing standards and adapted for individual and selective securement to the base unit in an operative position using at least one releasable connector. Each target chamber defines an enclosure, a media inlet to the enclosure, and an air exhaust vent, and each chamber includes a target specimen securement device for selectively and releasably securing a target specimen in an operative position in line with the target path so that testing media projected from an operatively secured media gun impinges on the operatively secured target specimen.
In accordance with yet another aspect of the present invention, a method of constructing a gravelometer apparatus to perform testing in accordance with one of at least two different testing standards includes selecting one of a plurality of different media projecting guns. Each of the guns is conformed in accordance with a different testing standard. The selected gun is operatively and releasably secured to a frame member. One of a plurality of different target chambers is selected to correspond with the selected one: of the media guns. Each chamber is conformed in accordance with one of the different testing standards. The selected chamber is operatively and releasably securing to the frame member so that a testing media outlet of the operatively secured media gun is directed into an enclosed interior portion of the operatively secured target chamber. An air inlet of the operatively secured media gun is connected to a supply of compressed air.
One advantage of the present invention is that it eliminates the need for multiple gravelometers each dedicated to a particular testing standard.
Another advantage of the present invention is that it provides a gravelometer base unit to which any one of a plurality of media guns and many one of a plurality of target chambers are easily and conveniently connected to construct a gravelometer in accordance with any testing standard.
Still another advantage of the present invention is that a three-dimensional specimen target chamber is easily and selectively connectable to any of the target chambers as needed for testing three-dimensional specimens in accordance with any testing standard.
Yet another advantage of the present invention is that a wide variety of blast media such as gravel, split shot, buckshot, sand, or MDOT 25A, is able to be used for testing procedures.
A further advantage of the present invention is that it is more easily and less expensively repaired or calibrated.
Still other benefits and advantages of the invention will become readily apparent to those skilled in the art upon reading and understanding the following detailed specification.